| Home | [11–20] << 21 22 23 24 25 26 27 28 29 30 >> [31–40] |
|
Viera, V. M., Nolan, P. M., Cote, S. D., Jouventin, P. & Groscolas, R. (2008). Is Territory Defence related to Plumage Ornaments in the King Penguin Aptenodytes patagonicus? Ethology, 114(2), 146–153.
Abstract: Colourful ornaments in monogamous birds may be directed at potential mates or other conspecifics to signal individual condition, reproductive status or fighting ability, especially in monogamous and territorial species. We investigated whether the size of the orange auricular patch may be an indicator of aggressiveness in the king penguin Aptenodytes patagonicus, a monogamous and territorial seabird. The relationship between auricular patch size and defence behaviour was explored relative to territory location (centre vs. periphery of the colony), period of reproduction (early vs. late), state of reproduction (incubation vs. brooding) and sex. The proportion of time spent in territorial defence and the rate of aggressive behaviours were positively correlated with auricular patch size, mainly because central birds were more aggressive than peripheral birds and also had larger patch sizes. The period of reproduction, state of reproduction and sex did not interact with patch size to affect aggressiveness. Our results suggest that the size of the auricular patch in king penguins may be a reliable signal allowing individuals to evaluate the quality of mates or competitors in terms of aggressiveness. Whether aggressiveness is directly linked to patch size or indirectly through body condition, however, remains to be determined. In any event, birds with larger patches seem to gain central territories in the colony, thereby increasing their reproductive success. Finally, our study adds to the growing evidence that the evolution of sexually monomorphic ornaments may stem from mutual sexual selection.
Programme: 119;354
|
|
Charmantier A, Buoro M, Gimenez O, Weimerskirch H,. (2011). Heritability of short-scale natal dispersal in a large-scale foraging bird, the wandering albatross
. J. Evol. Biol., 24(7), 1487–1496.
Abstract: Natal dispersal is a key life history trait for the evolution and adaptation of wild populations. Although its evolution has repeatedly been related to the social and environmental context faced by individuals, parentoffspring regressions have also highlighted a possible heritable component. In this study, we explore heritability of natal dispersal, at the scale of the sub-Antarctic Possession Island, for a large-scale foraging seabird, the Wandering albatross Diomedea exulans, exploiting a pedigree spanning over four decades and a maximum of four generations. The comparison of three different methods shows that heritability on the liability scale can vary drastically depending on the type of model (heritability from 6% to 86%), with a notable underestimation by restricted maximum likelihood animal models (6%) compared to Bayesian animal models (36%). In all cases, however, our results point to significant additive genetic variance in the individual propensity to disperse, after controlling for substantial effects of sex and natal colony. These results reveal promising evolutionary potential for short-scale natal dispersal, which could play a critical role for the long-term persistence of this species on the long run.
Keywords: Bayesian framework, heritability, liability to disperse, local scale, natal dispersal, seabird, threshold model,
Programme: 109
|
|
Authier M, Cam E, Guinet C,. (2011). Selection for increased body length in Subantarctic fur seals on Amsterdam Island
. J. Evol. Biol., 24(3), 607–616.
Abstract: The traditional distinction between ecological and evolutionary times is eroding, calling for tighter links between ecology and evolution. An example of such a brigde between the two disciplines is the so-called animal model, a methodology initially developed by animal breeders, which has become very popular among ecologists studying contemporary microevolution. Using a Bayesian multi-trait animal model, we investigated the quantitative genetics of body size, a fitness-related trait, in Subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island, Southern Ocean. Our approach jointly modelled the growth and selection processes at work in this population. Body length is heritable for both sexes, and females are under selection for increased body length in this population. We strongly suspect the peculiar ecological context of impoverished, suitable prey availability exacerbated by density-dependence phenomena to be an important selective agent on females breeding on Amsterdam Island.
Keywords: Bayesian, pinnipeds, quantitative genetics, selection,
Programme: 109
|
|
McCoy Karen D, . (2009). Host-parasite determinants of parasite population structure: lessons from bats and mites on the importance of time.
. Molecular ecology, 18(17), 3545–7.
Abstract: By definition, parasitic organisms are strongly dependant on their hosts, and for a great majority, this dependence includes host-to-host transmission. Constraints imposed by the host's spatial distribution and demography, in combination with those of the parasite, can lead to a metapopulation structure, where parasite populations are highly stochastic (i.e. prone to frequent extinctions and re-colonizations) and where drift becomes a major force shaping standing genetic variation. This, in turn, will directly affect the observed population structure, along with the ability of the parasite to adapt (or co-adapt) to its host. However, only a specific consideration of temporal dynamics can reveal the extent to which drift shapes parasite population structure; this is rarely taken into account in population genetic studies of parasitic organisms. The study by Bruyndonckx et al. in this issue of Molecular Ecology does just this and, in doing so, illustrates how a comparison of host-parasite co-structures in light of temporal dynamics can be particularly informative for understanding the ecological and evolutionary constraints imposed by the host. More specifically, the authors examine spatial and temporal population genetic data of a parasitic mite Spinturnix bechsteini that exclusively exploits the Bechstein's bat Myotis bechsteinii and consider these data in relation to host-parasite life histories and the population structure of the host.
Keywords: Animals, Chiroptera, Chiroptera: parasitology, Genetics, Population, Host-Parasite Interactions, Mites, Mites: genetics,
Programme: 333
|
|
de Dinechin M., Ottvall R., Quillfeldt P. & Jouventin P. (2009). Speciation chronology of rockhopper penguins inferred from molecular, geological and palaeoceanographic data. J. Biogeogr., 36(4), 693–702.
Abstract: Aim The Southern Ocean is split into several biogeographical provinces between convergence zones that separate watermasses of different temperatures. Recent molecular phylogenies have uncovered a strong phylogeographic structure among rockhopper penguin populations, Eudyptes chrysocome sensu lato, from different biogeographical provinces. These studies suggested a reclassification as three species in two major clades, corresponding, respectively, to warm, subtropical and cold sub-Antarctic watermasses rather than to geographic proximity. Such a phylogeographic pattern, also observed in plants, invertebrates and fishes of the Southern Ocean, suggests that past changes in the positions of watermasses may have affected the evolutionary history of penguins. We calculated divergence times among various rockhopper penguin clades and calibrated these data with palaeomagmatic and palaeoceanographic events to generate a speciation chronology in rockhopper penguins.Location Southern Ocean.Methods Divergence times between populations were calculated using five distinct mitochondrial DNA loci, and assuming a molecular clock model as implemented in mdiv. The molecular evolution rate of rockhopper penguins was calibrated using the radiochronological age of St Paul Island and Amsterdam Island in the southern Indian Ocean. Separations within other clades were correlated with palaeoceanographic data using this calibrated rate.Results The split between the Atlantic and Indian populations of rockhopper penguins was dated as 0.25 Ma, using the date of emergence of St Paul and Amsterdam islands, and the divergence between sub-Antarctic and subtropical rockhopper penguins was dated as c. 0.9 Ma (i.e. during the mid-Pleistocene transition, a major change in the Earth's climate cycles).Main conclusions The mid-Pleistocene transition is known to have caused a major southward shift in watermasses in the Southern Ocean, thus changing the environment around the northernmost rockhopper penguin breeding sites. This ecological isolation of northernmost populations may have caused vicariant speciation, splitting the species into two major clades. After the emergence of St Paul and Amsterdam islands in the subtropical Indian Ocean 0.25 Ma, these islands were colonized by penguins from the subtropical Atlantic, 6000 km away, rather than by penguins from the sub-Antarctic Indian Ocean, 5000 km closer.
Programme: 354
|
|
Gilg Olivier, Sittler Benoît, Hanski Ilkka. (2009). Climate change and cyclic predatorprey population dynamics in the high Arctic
. Glob Chang Biol, 15(11), 2634–2652.
Abstract: The high Arctic has the world's simplest terrestrial vertebrate predatorprey community, with the collared lemming being the single main prey of four predators, the snowy owl, the Arctic fox, the long-tailed skua, and the stoat. Using a 20-year-long time series of population densities for the five species and a dynamic model that has been previously parameterized for northeast Greenland, we analyzed the population and community level consequences of the ongoing and predicted climate change. Species' responses to climate change are complex, because in addition to the direct effects of climate change, which vary depending on species' life histories, species are also affected indirectly due to, e.g., predatorprey interactions. The lemmingpredator community exemplifies these complications, yet a robust conclusion emerges from our modeling: in practically all likely scenarios of how climate change may influence the demography of the species, climate change increases the length of the lemming population cycle and decreases the maximum population densities. The latter change in particular is detrimental to the populations of the predators, which are adapted to make use of the years of the greatest prey abundance. Therefore, climate change will indirectly reduce the predators' reproductive success and population densities, and may ultimately lead to local extinction of some of the predator species. Based on these results, we conclude that the recent anomalous observations about lack of cyclic lemming dynamics in eastern Greenland may well be the first signs of a severe impact of climate change on the lemmingpredator communities in Greenland and elsewhere in the high Arctic.
Keywords: Alopex lagopus, Arctic community, climate change, cyclic dynamics, Dicrostonyx groenlandicus, Greenland, Mustela erminea, Nyctea scandiaca, predatorprey interaction, Stercorarius longicaudus,
Programme: 1036
|
|
Wittlinger Gérard, Farra Véronique. (2012). Observation of low shear wave velocity at the base of the polar ice sheets: evidence for enhanced anisotropy
. Geophysical Journal International , 190 (1 ), 391–405 .
Abstract: We analyse seismic data from the broad-band stations located on the Antarctic and Greenland ice sheets to determine the large-scale seismic parameters of the polar ice sheets. The P-to-S converted waves at the ice/rock interface and inside the ice sheets and their multiples (the P receiver functions) are used to estimate the in situ P velocity Vp and the P-to-S velocity ratio Vp/Vs of the polar ice. The thickness of the whole ice layer is precisely known either from radio echo soundings or from ice core drillings allowing thus an accurate determination of Vp and Vp/Vs. At some places in and near the Wilkes Basin, a sedimentary layer is probably squeezed between the ice and the bedrock. We find that the polar ice caps have a two-layer structure, the upper layer of variable thickness about 2/3 of the total thickness with velocities very close to the ice standard values and the lower layer preserving a standard Vp but with about 25 per cent smaller shear wave velocity and a more or less constant thickness. The shear-velocity drop in the lower layer may be the evidence of a strong anisotropy induced by preferred orientation of ice crystals and by fine layering of soft and hard ice layers. A large variation of ice viscosity with depth is therefore expected and heterogeneous flowing of the polar ice sheet. This heterogeneous flowing may invalidate the use at great depth of the ice dating models based on monotonic layer thinning.
Programme: 906
|
|
Wookey James. (2012). Direct probabilistic inversion of shear wave data for seismic anisotropy
. Geophysical Journal International , 189 (2 ), 1025–1037 .
Abstract: Shear wave splitting is perhaps the most unambiguous signature of the effect of anisotropic materials on the propagation of seismic waves. It has been used extensively to study anisotropy in the Earth, at global scales from the inner core to the tectonics of the uppermost mantle and crust, and at smaller scales for imaging deformation in hydrocarbon reservoirs. Well-established techniques exist for measuring shear wave splitting in a single (three-component) seismogram and more recently these have been extended to treat shear wave splitting in a tomographic fashion: determining non-uniform anisotropic models using large data sets of splitting measurements. Here, I propose an extension to a recent shear wave splitting tomography methodology which incorporates the data analysis into the inversion itself. This methodology uses a non-linear neighbourhood algorithm inversion to explore the parameter space defined by an anisotropic model consisting of a number of uniform domains. Each candidate model is assessed by applying the splitting it predicts to the entire data set. This approach is computationally expensive, but is highly amenable to parallelization. I apply the methodology to three simple synthetic cases to demonstrate the utility of the method. Finally, I apply the approach to the problem of inferring two-layer anisotropy from SKS splitting, which is a commonly attempted problem in global seismology. This uses data from the seismic station EKTN, where two-layer splitting has been previously inferred. This highlights some of the inherent trade-offs with such studies, and emphasizes the need to incorporate extra information to resolve these. This method is applicable to shear wave anisotropy analysis in a broad range of settings from global to reservoir scale.
Programme: 133
|
|
International Association of Geomagnetism and Aeronomy Working Group V-MOD Participating members, Finlay C C, Maus S, Beggan C D, Bondar T N, Chambodut A, Chernova T A, Chulliat A, Golovkov V P, Hamilton B, Hamoudi M, Holme R, Hulot G, Kuang W, Langlais B, Lesur V, Lowes F J, Lühr H, Macmillan S, Mandea M, McLean S, Manoj C, Menvielle M, Michaelis I, Olsen N, Rauberg J, Rother M, Sabaka T J, Tangborn A, Tøffner-Clausen L, Thébault E, Thomson A W P, Wardinski I, Wei Z, Zvereva T I, . (2010). International Geomagnetic Reference Field: the eleventh generation
. Geophysical Journal International, 183(3), 1216–1230.
Abstract: SUMMARY The eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy Working Group V-MOD. It updates the previous IGRF generation with a definitive main field model for epoch 2005.0, a main field model for epoch 2010.0, and a linear predictive secular variation model for 2010.02015.0. In this note the equations defining the IGRF model are provided along with the spherical harmonic coefficients for the eleventh generation. Maps of the magnetic declination, inclination and total intensity for epoch 2010.0 and their predicted rates of change for 2010.02015.0 are presented. The recent evolution of the South Atlantic Anomaly and magnetic pole positions are also examined.
Keywords: Magnetic field, Satellite magnetics,
Programme: 139;905
|
|
Callot J.P. & Geoffroy L. (2004). Magma flow in the East Greenland dyke swarm inferred from AMS study: Magmatic growth of volcanic margin. Geophysical journal international, 159(2), 816–830.
Abstract: Volcanic passive margins (VPMs) are characterized by large volumes of melt emplaced within the lithosphere during break-up processes. Several data and a recently proposed conceptual model of volcanic margin development suggest that VPMs are fed from localized crustal zones of magma storage, underlying large polygenetic volcanoes localized above diapir-like instabilities of the asthenosphere. We investigated the magma flow pattern within the coast-parallel dyke swarm of the East Greenland VPM, which is the only outcropping VPM, over a distance of 125 km. The 44 sampled dykes are representative of the successive families of intrusions. Igneous petrofabrics are constrained by the measurements of the anisotropy of magnetic susceptibility. The magnetic fabrics are of medium to low anisotropy (P' < 1.08) and show moderately oblate ellipsoids (T > 0) . Flow-related fabrics are recorded in 75 per cent of the sampled dykes. We infer the flow directions from the imbrication geometry of the magnetic foliation planes at the dyke margins, and check the results by measuring the preferred orientation of plagioclase in thin sections cut in the magnetic principal planes. Due to probable fabric superposition, the magnetic lineation represents the zone axis for the distribution of magnetic foliation plane. We obtained 23 reliable flow directions that are predominantly horizontal and directed away from identified crustal reservoirs. This flow pattern supports the proposed model of VPM growth, and emphasizes the localized nature of the magma sources in the mantle. The entire flood basalt sequence appears to have been fed by a restricted number of crustal reservoirs and associated dyke swarms.
Programme: 290
|